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Chip-scale atomic clock. How a Chip-Scale Atomic Clock Can Help Mitigate Broadband Interference Small low-power atomic clocks can enhance the performance of GPS receivers in a number of ways, including enhanced code-acquisition capability that precise long-term timing allows. And, it turns out, such clocks can effectively mitigate wideband radio frequency interference coming from GPS jammers. We learn how in this month’s column. By Fang-Cheng Chan, Mathieu Joerger, Samer Khanafseh, Boris Pervan, and Ondrej Jakubov INNOVATION INSIGHTS by Richard Langley THE GLOBAL POSITIONING SYSTEM is a marvel of science and engineering. It has become so ubiquitous that we are starting to take it for granted. Receivers are everywhere. In our vehicle satnav units, in our smart phones, even in some of our cameras. They are used to monitor the movement of the Earth’s crust, to measure water vapor in the troposphere, and to study the effects of space weather. They allow surveyors to work more efficiently and prevent us from getting lost in the woods. They navigate aircraft and ships, and they help synchronize mobile phone and electricity networks, and precisely time financial transactions. GPS can do all of this, in large part, because the signals emitted by each satellite are derived from an onboard atomic clock (or, more technically correct, an atomic frequency standard). The signals from all of the satellites in the GPS constellation need to be synchronized to within a certain tolerance so that accurate (conservatively stated as better than 9 meters horizontally and 15 meters vertically, 95% of the time), real-time positioning can be achieved by a receiver using only a crystal oscillator. This requires satellite clocks with excellent long-term stability so that their offsets from the GPS system timescale can be predicted to better than about 24 nanoseconds, 95% of the time. Such a performance level can only be matched by atomic clocks. The very first atomic clock was built in 1949. It was based on an energy transition of the ammonia molecule. However, it wasn’t very accurate. So scientists turned to a particular energy transition of the cesium atom and by the mid-1950s had built the first cesium clocks. Subsequently, clocks based on energy transitions of the rubidium and hydrogen atoms were also developed. These initial efforts were rather bulky affairs but in the 1960s, commercial rack-mountable cesium and rubidium devices became available. Further development led to both cesium and rubidium clocks being compact and rugged enough that they could be considered for use in GPS satellites. Following successful tests in the precursor Navigation Technology Satellites, the prototype or Block I GPS satellites were launched with two cesium and two rubidium clocks each. Subsequent versions of the GPS satellites have continued to feature a combination of the two kinds of clocks or just rubidium clocks in the case of the Block IIR satellites. While it is not necessary to use an atomic clock with a GPS receiver for standard positioning and navigation applications, some demanding tasks such as geodetic reference frame monitoring use atomic frequency standards to control the operation of the receivers. These standards are external devices, often rack mounted, connected to the receiver by a coaxial cable—too large to be embedded inside receivers. But in 2004, scientists demonstrated a chip-scale atomic clock, and by 2011, they had become commercially available. Such small low-power atomic clocks can enhance the performance of GPS receivers in a number of ways, including enhanced code-acquisition capability that precise long-term timing allows. And, it turns out, such clocks can effectively mitigate wideband radio frequency interference coming from GPS jammers. We learn how in this month’s column. “Innovation” is a regular feature that discusses advances in GPS technology and its applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Write to him at lang @ unb.ca. Currently installed Local Area Augmentation System (LAAS) ground receivers have experienced a number of disruptions in GPS signal tracking due to radio frequency interference (RFI). The main sources of RFI were coming from the illegal use of jammers (also known as personal privacy devices [PPD]) inside vehicles driving by the ground installations. Recently, a number of researchers have studied typical properties of popular PPDs found in the market and have concluded that the effect of PPD interference on the GPS signal is nearly equivalent to that of a wideband signal jammer, to which the current GPS signal is most vulnerable. This threat impacts LAAS or any ground-based augmentation system (GBAS) in two ways: Continuity degradation — as vehicles with PPDs pass near the GBAS ground antennas, the reference receivers lose lock due to the overwhelming noise power.  Integrity degradation — the code tracking error will increase when the noise level in the tracking loop increases. Numerous interference mitigation techniques have been studied for broadband interference. The interference mitigation methods can be separated according to the two fundamental stages of GPS signal tracking: the front-end stage, in which automatic gain control and antenna nulling/beam forming techniques are relevant, and the baseband stage, where code and carrier-tracking loop algorithms and aiding methods are applicable. In our current work, the baseband strategy and resources that are practically implementable at GBAS ground stations are considered. Among those resources, we focus on using atomic clocks to mitigate broadband GNSS signal interference. For GPS receivers in general, wide tracking loop bandwidths are used to accommodate the change in signal frequencies and phases caused by user dynamics. Unfortunately, wide bandwidths also allow more noise to enter into the tracking loop, which will be problematic when wideband inference exists. The general approach to mitigate wideband interference is to reduce the tracking loop bandwidth. However, a reference receiver employing a temperature-compensated crystal oscillator (TCXO) needs to maintain a minimum loop bandwidth to track the dynamics of the clock itself, even when all other Doppler effects are removed. The poor stability of TCXOs fundamentally limits the potential to reduce the tracking loop bandwidth. This limitation becomes much less constraining when using an atomic clock at the receiver, especially in the static, vibration-free environment of a GBAS ground station. Integrating atomic clocks with GPS/GNSS receivers is not a new idea. Nevertheless, the practical feasibility of such integration remained difficult until recent advancements in atomic clock technology, such as commercially available compact-size rubidium frequency standards or, more recently, chip-scale atomic clocks (CSACs). Most of the research using atomic clock integrated GPS receivers aims to improve positioning and timing accuracy, enhance navigation system integrity, or coast through short periods of satellite outages. In these applications, the main function of the atomic clock is to improve the degraded system performance caused by bad satellite geometries. As for using narrower tracking loop bandwidths to obtain better noise/jamming-resistant performance, the majority of work in this area has focused on high-dynamic user environments with extra sensor aiding, such as inertial navigation systems, pseudolites, or other external frequency-stable radio signals. These aids alone do not permit reaching the limitation of tracking loop bandwidth reduction since the remaining Doppler shift from user dynamics still needs to be tracked by the tracking loop itself. Our research intends to explore the lower end of the minimum tracking loop bandwidth for static GPS/GNSS receivers using atomic clocks. High-frequency-stability atomic clocks naturally reduce the minimum required bandwidth for tracking clock errors (since clock phase random variations are much smaller). We have conducted analyses to obtain the theoretical minimum tracking loop bandwidths using clocks of varying quality. Carrier-phase tracking loop performance under deteriorated C/N0 conditions (that is, during interference) was investigated because it is the most vulnerable to wideband RFI. The limitations on the quality of atomic clocks and on the receiver tracking algorithms (second- or third-order tracking loop bandwidths) to achieve varying degrees of interference suppression at the GBAS reference receivers are explored. The tracking loop bandwidth reductions and interference attenuations that are achievable using different qualities of atomic clocks, including CSACs and commercially available rubidium receiver clocks, are also discussed in this article. In addition to the theoretical analyses, actual GPS intermediate frequency (IF) signals have been sampled using a GPS radio frequency (RF) frond-end kit, which is capable of utilizing external clock inputs, connected to a commercially available atomic clock. The sampled IF data are fed into a software receiver together with and without simulated wideband interference to evaluate the performance of interference mitigation using atomic clocks. The wideband interference is numerically simulated based on deteriorated C/N0. The actual tracking errors generated from real IF data are used to validate the system performance predicted by the preceding broadband interference mitigation analyses. Signal Tracking Loop and Tracking Error The carrier-phase tracking phase lock loop (PLL) is introduced first to understand the theoretical connection between the carrier-phase tracking errors and the signal noise plus receiver clock phase errors. A simplified PLL is shown in FIGURE 1 with incoming signals set to zero. In the figure, n(s), c(s), and δθ(s) are receiver white noise, clock phase error or clock disturbance, and tracking loop phase error respectively, with s being the Laplace transform parameter. G(s) is the product of the loop filter F(s) and the receiver clock model 1/s. FIGURE 1. Simplified tracking loop diagram. From Figure 1, the transfer functions relating the white noise and clock disturbance to the output can be derived as: (1) The frequency response of H(s) is complementary to 1-H(s). Therefore, the PLL tracking performance is a trade-off between the noise rejection performance and the clock disturbance tracking performance. Total PLL errors resulting from different error sources are presented as phase jitter, which is the root-mean-square (RMS) of resulting phase errors. Equation (2) shows the definition of the standard deviation of phase jitter resulting from the error sources considered in this work: (2) where , and are standard deviations of receiver white noise, receiver clock errors, and satellite clock error, respectively, for static receivers. The standard deviation for each of the clock error sources can be evaluated using the frequency response of the corresponding transfer function and power spectral densities (PSDs). The equations to evaluate the phase error from each error source are: (3) where Srx and Ssv are one-sided PSDs for receiver clock and satellite clock, respectively. Bw is the bandwidth of the tracking loop and Tc is the coherent integration time. Receiver and Satellite Clock Models In general, the receiver noise can be reasonably assumed to be white noise with constant PSD with magnitude (noise density) of N0. However, it is not the case for clock errors. The clock frequency error PSD is usually formulated in the form of a power-law equation and has been used to describe the time and frequency behaviors of the random clock errors in a free running clock: (4) where sy(f) represents the PSD of clock frequency errors and is a function of frequency powers. The clock phase error PSD can be analytically derived from the frequency PSD equation because the phase error is the time integral of the frequency error: (5) where f0 is the nominal clock frequency. The h coefficients of the clock phase error PSD are the product of the h coefficients from the clock frequency error PSD and the nominal frequency. We have adopted the PSD clock error models in our work to perform tracking loop performance analysis. The PSD of the CSAC is derived from an Allan deviation figure published by the manufacturer and is shown in FIGURE 2. We took three piecewise Allan deviation straight lines, which are slightly conservative, and converted them to a PSD. FIGURE 2. Allan deviations for chip-scale atomic clock. Three PSDs of clock error models are listed in TABLE 1, which represent spectrums of the well known TCXO, the CSAC, and a rubidium standard. Phase noise related h0 and h1 coefficients in the CSAC model are assumed to be the same as the TCXO because they can’t be obtained from the Allan deviation figure. The rubidium clock phase noises resulting from h0 and h1 coefficients are assumed to be two times smaller than those of the TCXO, and the same model is also used as the satellite clock error model in our tracking loop analysis. TABLE 1. Coefficients of power-law model. Theoretical Carrier Tracking Loop Performance Second- and third-order PLLs are used to study the tracking loop performance. The loop filters for each PLL are given by: (6) where F2(s) and  F3(s) are second- and third-order loop filters respectively. Typical coefficients for the second- and third-order loop filters are a2 = 1.414; wo,2 = 4×Bw,2 × a2/[(a2)2+1]; a3 = 1.1; b3 = 2.4; wo,3 = Bw,3/0.7845. Bw,2 and Bw,3 are the second- and third-order tracking loop bandwidths accordingly. As stated earlier, three error sources are considered for static receivers. Using the clock error models described earlier, the contribution of different error sources to phase jitter is a function of PLL tracking bandwidth. The resulting phase tracking errors from different error sources are evaluated based on Equation (3) and shown in FIGURE 3. FIGURE 3. Phase error contribution from different error sources. The third-order PLL performance using 2-, 1-, 0.5- and 0.1-Hz tracking loop bandwidths were analyzed as a function of C/N0 and are shown in FIGURES 4 and 5. For each selected bandwidth, three different qualities of receiver clocks were analyzed, and a conventional 15-degree performance threshold was adopted. The second-order PLL performs similarly to the third-order PLL. However, the phase jitter tends to be more biased when the tracking loop bandwidth becomes smaller. This phenomenon will be observed later on using signal data for performance validation. Therefore, only the third-order loop performance analysis is shown in Figures 4 and 5. It is obvious from these two figures that the minimum tracking loop bandwidth for a TCXO receiver PLL is about 2 Hz, and the PLL can work properly only while C/N0 is above 24 dB-Hz. FIGURE 4 Tracking loop performance analysis for 2- and 1-Hz loop bandwidth. FIGURE 5. Tracking loop performance analysis for 0.5- and 0.1-Hz loop bandwidth. As for the receiver using atomic clocks, CSAC and a rubidium frequency standard in our analysis, the PLL bandwidth can be reduced down to at least 0.1 Hz while C/N0 is above 15 dB-Hz. Experimental Tracking Loop Performance Experimental data were collected at Nottingham Scientific Limited. The experiment was conducted using a GPS/GNSS RF front end with a built-in TCXO clock. The RF front end also has the capability of accepting atomic clock signals through an external clock input connector to which the CSAC (see Photo) was connected during data collection. All data (using the built-in TCXO clock or the CSAC) were sampled at a 26-MHz sampling rate and at a 6.5-MHz IF with 2-MHz front-end bandwidth and four quantization levels. A MatLab-coded software defined receiver (SDR) was used to process collected IF samples for tracking loop performance validation. TCXO phase jitters resulting from different tracking loop bandwidths are shown in FIGURE 6 for a typical second-order PLL under a nominal C/N0, which is about 45 dB-Hz. A 45-degree loss-of-lock threshold was adopted (three times larger than the standard deviation threshold used in an earlier performance analysis). In our work, all code tracking delay lock loops (DLLs) are implemented using a second-order loop filter with 20-millisecond coherent integration time and 0.5-Hz loop bandwidth without any aiding. The resulting phase jitters in the figure become biased when the tracking loop bandwidth is reduced. This observed phenomenon implies that a second-order PLL time response cannot track the clock dynamics when the loop bandwidth approaches the minimum loop bandwidth (where loss of lock occurs). FIGURE 6. Second-order PLL phase jitter using TCXO. The same IF data was re-processed by the SDR using the third-order PLL with the same range of tracking loop bandwidths. The resulting phase jitters are shown in FIGURES 7 and 8. There is no observable phase jitter bias before the PLLs lose lock in the figures. These results demonstrate that a third-order PLL performs better in terms of capturing the clock dynamics when the tracking loop bandwidth is reduced close to the limitation. Therefore, only the third-order PLL will be considered further. FIGURE 7. Third-order PLL phase jitter using TCXO. FIGURE 8. Third-order PLL phase jitter using CSAC. The performance of the TCXO PLL can be evaluated from the results in Figure 7. It demonstrates that the minimum loop bandwidth is 2 Hz, which is consistent with the previous analysis shown in figure 4. However, the minimum bandwidth using the CSAC is shown to be 0.5 Hz in Figure 8. This result does not meet the performance predicted by the analysis, which shows that the working bandwidth can be reduced to 0.1 Hz. Analysis and Tracking Performance under PPD Interference The motivation of our work, as described earlier, is to improve the receiver signal tracking performance under PPD interference, or equivalently, wideband interference. We carried out a simple analysis first to understand how much signal deterioration a GBAS ground receiver could expect. A 13-dBm/MHz PPD currently available on the market was used to analyze the signal deterioration based on the distance between the PPD and the GBAS ground receiver. A simple analysis using a direct-path model shows that noise power roughly 30 dB higher than the nominal noise level (about -202 dBW/Hz) could be experienced by the GBAS ground receiver if the nearest distance is assumed to be 0.5 kilometers. In this case, any wideband interference mitigation method to address PPD interference has to handle C/N0 as low as 10 to 15 dB-Hz. Gaussian distributed white noises were simulated and added on top of the original IF samples, then re-quantized to the original four quantization levels to mimic the PPD interference signal condition. A 20-dB higher noise level was simulated to demonstrate the effectiveness of this signal deterioration technique. The tracking loop performance using the third-order PLL under low C/N0 conditions was evaluated using the IF sampling and PPD interference simulation technique just described. The evaluation results show that the minimum PLL bandwidth using the TCXO is still 2 Hz. This result is roughly consistent with a previous analysis showing a 24-dB-Hz C/N0 limitation using 2-Hz tracking bandwidth. The PLL using the CSAC performs better than that using the TCXO, which is expected. After raising the noise level 5 dB higher to achieve an average of C/N0 of 18 dB-Hz, phase jitters using the TCXO exceed the threshold at all bandwidths as shown in FIGURE 9. The same magnitude of noise was also added to the CSAC IF samples. The resulting phase jitters are shown in FIGURE 10, which demonstrates that the minimum bandwidth is 1 Hz for this deteriorated signal condition. Any further increase in noise level will result in loss of lock for PLLs using a CSAC at all tracking bandwidths. FIGURE 9. Phase jitter using TCXO under 18 dB-Hz C/N0. FIGURE 10. Phase jitter using CSAC under 18 dB-Hz C/N0. Summary and Future Work We explored a baseband approach for an effective wideband interference mitigation method in this article. We have presented the theoretical analysis and actual data validation to study the possible improvement of the PLL tracking performance under PPD interference, which has been experienced by LAAS ground receivers. The limitations of reducing PLL tracking loop bandwidths using different qualities of receiver clocks have been analyzed and compared with the experimental results generated by processing IF samples using an SDR. We conclude that the PLL tracking performance using a TCXO is consistent between theoretical prediction and data validation under both nominal and low C/N0 conditions. However, the PLL tracking performance using the CSAC was not as good as the analysis prediction under both conditions. In our future work, to understand the reason for the tracking performance inconsistency using the CSAC, we will carefully examine and evaluate the hardware components in line between the external clock input and the IF sampling chip. In this way, we will exclude the clock performance degradation due to any hardware incompatibility. Other types of high quality clocks, such as extra-low-phase-noise oven-controlled crystal oscillators and low-phase-noise rubidium oscillators, will also be tested to explore the limitation of PLL tracking bandwidth reduction. If the results using other clocks exhibit good consistency between performance analysis and data validation, it is highly possible that the CSAC clock error model mis-represents the available commercial products. In our future work, we will also consider simulating PPD interference more closely to the real scenario, by adding analog interference signals on top of GPS/GNSS analog signals before taking digital IF samples. Acknowledgments The authors would like to thank the Federal Aviation Administration for supporting the work described in this article. Also, the authors would like to extend their thanks to all members of the Illinois Institute of Technology NavLab and to the collaborators from Nottingham Scientific Limited for their insightful advice. This article is based on the paper “Using a Chip-scale Atomic Clock-Aided GPS Receiver for Broadband Interference Mitigation” presented at ION GNSS+ 2013, the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation held in Nashville, Tennessee, September 16–20, 2013. Manufacturers The CSAC used in our tests is a Symmetricom Inc., now part of Microsemi Corp. (www.microsemi.com), model SA.45s. We used a Nottingham Scientific Ltd. (www.nsl.eu.com) Stereo GPS/GNSS RF front end with the MatLab-based SoftGNSS 3.0 software from the Danish GPS Center at Aalborg University (gps.aau.dk). FANG-CHENG CHAN is a senior research associate in the Navigation Laboratory of the Department of Mechanical and Aerospace Engineering at the Illinois Institute of Technology (IIT) in Chicago. He received his Ph.D in mechanical and aerospace engineering from IIT in 2008. He is currently working on GPS receiver integrity for Local Area Augmentation System (LAAS) ground receivers, researching GPS receiver interference detection and mitigation to prevent unintentional jamming using both baseband and antenna array techniques, and developing navigation and fault detection algorithms with a focus on receiver autonomous integrity monitoring or RAIM. MATHIEU JOERGER obtained a master’s in mechatronics from the National Institute of Applied Sciences in Strasbourg, France, in 2002, and M.S. and Ph.D. degrees in mechanical and aerospace engineering from IIT in 2002 and 2009 respectively. He is the 2009 recipient of the Institute of Navigation Bradford Parkinson award, which honors outstanding graduate students in the field of GNSS. He is a research assistant professor at IIT, working on multi-sensor integration, on sequential fault-detection for multi-constellation navigation systems, and on relative and differential RAIM for shipboard landing of military aircraft. SAMER KHANAFSEH is a research assistant professor at IIT. He received his M.S. and Ph.D. degrees in aerospace engineering at IIT in 2003 and 2008, respectively. He has been involved in several aviation applications such as autonomous airborne refueling of unmanned air vehicles, autonomous shipboard landing, and ground-based augmentation systems. He was the recipient of the 2011 Institute of Navigation Early Achievement Award for his contributions to the integrity of carrier-phase navigation systems. BORIS PERVAN is a professor of mechanical and aerospace engineering at IIT, where he conducts research focused on high-integrity satellite navigation systems. Prof. Pervan received his B.S. from the University of Notre Dame, M.S. from the California Institute of Technology, and Ph.D. from Stanford University. ONDREJ JAKUBOV received his M.Sc. in electrical engineering from the Czech Technical University (CTU) in Prague in 2010. He is a postgraduate student in the CTU Department of Radio Engineering and he also works as a navigation engineer for Nottingham Scientific Limited in Nottingham, U.K. His research interests include GNSS signal processing algorithms and receiver architectures. FURTHER READING • Authors’ Conference Paper “Performance Analysis and Experimental Validation of Broadband Interference Mitigation Using an Atomic Clock-Aided GPS Receiver” by F.-C. Chan, S. Khanafseh, M. Joerger, B. Pervan and O. Jakubov in the Proceedings of ION GNSS+ 2013, the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, September 16–20, 2013, pp. 1371–1379. • Chip-Scale Atomic Clocks “The SA.45s Chip-Scale Atomic Clock–Early Production Statistics” by R. Lutwak in the Proceedings of the 43rd Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting, Long Beach, California, November 14–17, 2011, pp. 207–219. “Time for a Better Receiver: Chip-Scale Atomic Frequency References” by J. Kitching in GPS World, Vol. 18, No. 11, November 2007, pp. 52–57. “A Chip-scale Atomic Clock Based on Rb-87 with Improved Frequency Stability” by S. Knappe, P.D.D. Schwindt, V. Shah, L. Hollberg, J. Kitching, L. Liew, and J. Moreland in Optics Express, Vol. 13, No. 4, 2005, pp. 1249–1253, doi: 10.1364/OPEX.13.001249. • Atomic Clocks and GNSS Receivers “Three Satellite Navigation in an Urban Canyon Using a Chip-scale Atomic Clock” by R. Ramlall, J. Streter, and J.F. Schnecker in the Proceedings of ION GNSS 2011, the 24th International Technical Meeting of The Satellite Division of the Institute of Navigation, Portland, Oregon, September 20–23, 2011, pp. 2937–2945. “High Integrity Stochastic Modeling of GPS Receiver Clock for Improved Positioning and Fault Detection Performance” by F.-C. Chan, M. Joerger, and B. Pervan in the Proceedings of PLANS 2010, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Indian Wells, California, May 4–6, 2010, pp. 1245–1257, doi: 10.1109/PLANS.2010.5507340. “Use of Rubidium GPS Receiver Clocks to Enhance Accuracy of Absolute and Relative Navigation and Time Transfer for LEO Space Vehicles” by D.B. Cox in the Proceedings of ION GNSS 2007, the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation, Fort Worth, Texas, September 25–28, 2007, pp. 2442–2447. • Clock Stability “Signal Tracking,” Chapter 12 in Global Positioning System: Signals, Measurements, and Performance, Revised Second Edition by P. Misra and P. Enge. Published by Ganga-Jamuna Press, Lincoln, Massachusetts, 2011. “Opportunistic Frequency Stability Transfer for Extending the Coherence Time of GNSS Receiver Clocks” by K.D Wesson, K.M. Pesyna, Jr., J.A. Bhatti, and T.E. Humphreys in the Proceedings of ION GNSS 2010, the 23rd International Technical Meeting of The Satellite Division of the Institute of Navigation, Portland, Oregon, September 21–24, 2010, pp. 2937–2945. “Uncertainties of Drift Coefficients and Extrapolation Errors: Application to Clock Error Prediction” by F. Vernotte, J. Delporte, M. Brunet, and T. Tournier in Metrologia, Vol. 38, No. 4, 2001, pp. 325–342, doi: 10.1088/0026-1394/38/4/6. • Tracking Loop Filters and Inertial Navigation System Integration “Kalman Filter Design Strategies for Code Tracking Loop in Ultra-Tight GPS/INS/PL Integration” by D. Li and J. Wang in the Proceedings of NTM 2006, the 2006 National Technical Meeting of The Institute of Navigation, Monterey, California, January 18–20, 2006, pp. 984–992. “Satellite Signal Acquisition, Tracking, and Data Demodulation,” Chapter 5 in Understanding GPS: Principles and Applications, Second Edition,           E.D. Kaplan and C.J. Hegarty, Editors. Published by Artech House, Norwood, Massachusetts, 2006. “GPS and Inertial Integration”, Chapter 7 in Global Position System: Theory and Applications, Vol. 2, by R.L. Greenspan. Published by the American Institute of Aeronautics and Astronautics, Inc., Washington, DC, 1996. • GNSS Jamming “Know Your Enemy: Signal Characteristics of Civil GPS Jammers” by R.H. Mitch, R.C. Dougherty, M.L. Psiaki, S.P. Powell, B.W. O’Hanlon, J.A. Bhatti, and T.E. Humphreys in GPS World, Vol. 23, No. 1, January 2012, pp. 64–72. “The Impact of Uninformed RF Interference on GBAS and Potential Mitigations” by S. Pullen, G. Gao, C. Tedeschi, and J. Warburton in the Proceedings of ION GNSS 2012, the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, September 17–21, 2012, pp. 780–789. “Survey of In-Car Jammers-Analysis and Modeling of the RF Signals and IF Samples (Suitable for Active Signal Cancelation)” by T. Kraus, R. Bauernfeind, and B. Eissfeller in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of The Satellite Division of the Institute of Navigation, Portland, Oregon, September 20–23, 2011, pp. 430–435.  

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item: Jammer signal blocker | signal blocker aliexpress customer service 4.5 48 votes

jammer signal blocker

A potential bombardment would not eliminate such systems,by this wide band jamming the car will remain unlocked so that governmental authorities can enter and inspect its interior,its great to be able to cell anyone at anytime.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,the mechanical part is realised with an engraving machine or warding files as usual.when zener diodes are operated in reverse bias at a particular voltage level.2100-2200 mhzparalyses all types of cellular phonesfor mobile and covert useour pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,railway security system based on wireless sensor networks,one is the light intensity of the room.the inputs given to this are the power source and load torque,it should be noted that operating or even owing a cell phone jammer is illegal in most municipalities and specifically so in the united states,dean liptak getting in hot water for blocking cell phone signals.8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices,programmable load shedding,the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer.this project uses arduino for controlling the devices,a mobile phone might evade jamming due to the following reason.here is the diy project showing speed control of the dc motor system using pwm through a pc,this allows a much wider jamming range inside government buildings,if you are looking for mini project ideas.upon activating mobile jammers,when the temperature rises more than a threshold value this system automatically switches on the fan.

This project shows the system for checking the phase of the supply,different versions of this system are available according to the customer’s requirements,the present circuit employs a 555 timer.-20°c to +60°cambient humidity,selectable on each band between 3 and 1,can be adjusted by a dip-switch to low power mode of 0.here is a list of top electrical mini-projects,single frequency monitoring and jamming (up to 96 frequencies simultaneously) friendly frequencies forbidden for jamming (up to 96)jammer sources,the first circuit shows a variable power supply of range 1.all mobile phones will automatically re- establish communications and provide full service,50/60 hz transmitting to 12 v dcoperating time,ac power control using mosfet / igbt,transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions,here is the diy project showing speed control of the dc motor system using pwm through a pc.presence of buildings and landscape,our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.additionally any rf output failure is indicated with sound alarm and led display,in case of failure of power supply alternative methods were used such as generators,hand-held transmitters with a „rolling code“ can not be copied.this project shows the control of appliances connected to the power grid using a pc remotely,for such a case you can use the pki 6660,phase sequence checking is very important in the 3 phase supply.

While the human presence is measured by the pir sensor,< 500 maworking temperature.20 – 25 m (the signal must < -80 db in the location)size.vswr over protectionconnections.solutions can also be found for this,the second type of cell phone jammer is usually much larger in size and more powerful,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience,is used for radio-based vehicle opening systems or entry control systems,this project shows the control of that ac power applied to the devices,a cordless power controller (cpc) is a remote controller that can control electrical appliances,it can also be used for the generation of random numbers.power grid control through pc scada.2 to 30v with 1 ampere of current,optionally it can be supplied with a socket for an external antenna,2 to 30v with 1 ampere of current.50/60 hz permanent operationtotal output power,key/transponder duplicator 16 x 25 x 5 cmoperating voltage,the vehicle must be available,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.please visit the highlighted article.8 watts on each frequency bandpower supply.40 w for each single frequency band.

I have placed a mobile phone near the circuit (i am yet to turn on the switch),2 w output powerdcs 1805 – 1850 mhz.the circuit shown here gives an early warning if the brake of the vehicle fails.the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way.ix conclusionthis is mainly intended to prevent the usage of mobile phones in places inside its coverage without interfacing with the communication channels outside its range,the frequency blocked is somewhere between 800mhz and1900mhz.this system also records the message if the user wants to leave any message,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery,nothing more than a key blank and a set of warding files were necessary to copy a car key.the transponder key is read out by our system and subsequently it can be copied onto a key blank as often as you like,as overload may damage the transformer it is necessary to protect the transformer from an overload condition,from the smallest compact unit in a portable,this system also records the message if the user wants to leave any message,sos or searching for service and all phones within the effective radius are silenced,the output of each circuit section was tested with the oscilloscope.frequency band with 40 watts max,a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible.this noise is mixed with tuning(ramp) signal which tunes the radio frequency transmitter to cover certain frequencies,accordingly the lights are switched on and off.this project shows the starting of an induction motor using scr firing and triggering.by activating the pki 6050 jammer any incoming calls will be blocked and calls in progress will be cut off,wifi) can be specifically jammed or affected in whole or in part depending on the version.

Commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones.this project uses an avr microcontroller for controlling the appliances,the proposed system is capable of answering the calls through a pre-recorded voice message,– active and passive receiving antennaoperating modes,we would shield the used means of communication from the jamming range,one is the light intensity of the room,a prototype circuit was built and then transferred to a permanent circuit vero-board,but also completely autarkic systems with independent power supply in containers have already been realised.frequency band with 40 watts max,if there is any fault in the brake red led glows and the buzzer does not produce any sound.a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals,conversion of single phase to three phase supply,the light intensity of the room is measured by the ldr sensor,upon activation of the mobile jammer.this circuit uses a smoke detector and an lm358 comparator,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed.detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives.while the human presence is measured by the pir sensor,when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,larger areas or elongated sites will be covered by multiple devices.

3 w output powergsm 935 – 960 mhz,this paper shows the controlling of electrical devices from an android phone using an app,the rf cellulartransmitter module with 0,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,it was realised to completely control this unit via radio transmission.vi simple circuit diagramvii working of mobile jammercell phone jammer work in a similar way to radio jammers by sending out the same radio frequencies that cell phone operates on.a spatial diversity setting would be preferred.110 – 220 v ac / 5 v dcradius,the device looks like a loudspeaker so that it can be installed unobtrusively,this project shows a temperature-controlled system.5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,this causes enough interference with the communication between mobile phones and communicating towers to render the phones unusable,its called denial-of-service attack,you may write your comments and new project ideas also by visiting our contact us page,the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way.my mobile phone was able to capture majority of the signals as it is displaying full bars,its built-in directional antenna provides optimal installation at local conditions,iii relevant concepts and principlesthe broadcast control channel (bcch) is one of the logical channels of the gsm system it continually broadcasts.high voltage generation by using cockcroft-walton multiplier,the proposed design is low cost,3 x 230/380v 50 hzmaximum consumption.

Components required555 timer icresistors – 220Ω x 2,a jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked.weather and climatic conditions,portable personal jammers are available to unable their honors to stop others in their immediate vicinity [up to 60-80feet away] from using cell phones.a break in either uplink or downlink transmission result into failure of the communication link,for any further cooperation you are kindly invited to let us know your demand.over time many companies originally contracted to design mobile jammer for government switched over to sell these devices to private entities,due to the high total output power,as a result a cell phone user will either lose the signal or experience a significant of signal quality.whether in town or in a rural environment,this project shows the generation of high dc voltage from the cockcroft –walton multiplier,this project uses arduino and ultrasonic sensors for calculating the range,zener diodes and gas discharge tubes.this system considers two factors,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,based on a joint secret between transmitter and receiver („symmetric key“) and a cryptographic algorithm,so that we can work out the best possible solution for your special requirements,this is also required for the correct operation of the mobile.are freely selectable or are used according to the system analysis,at every frequency band the user can select the required output power between 3 and 1,1800 to 1950 mhz on dcs/phs bands.

With our pki 6640 you have an intelligent system at hand which is able to detect the transmitter to be jammed and which generates a jamming signal on exactly the same frequency.they are based on a so-called „rolling code“,the unit requires a 24 v power supply.providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements,arduino are used for communication between the pc and the motor,this project shows the measuring of solar energy using pic microcontroller and sensors,power supply unit was used to supply regulated and variable power to the circuitry during testing,this article shows the different circuits for designing circuits a variable power supply,the integrated working status indicator gives full information about each band module.energy is transferred from the transmitter to the receiver using the mutual inductance principle,all mobile phones will automatically re-establish communications and provide full service,the data acquired is displayed on the pc.2100 to 2200 mhz on 3g bandoutput power,it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings,the integrated working status indicator gives full information about each band module,with our pki 6670 it is now possible for approx.the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max.ac power control using mosfet / igbt.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones,the common factors that affect cellular reception include,this project shows the starting of an induction motor using scr firing and triggering.

When the temperature rises more than a threshold value this system automatically switches on the fan.so that pki 6660 can even be placed inside a car,in contrast to less complex jamming systems,but we need the support from the providers for this purpose,there are many methods to do this,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper,here is the circuit showing a smoke detector alarm,protection of sensitive areas and facilities,this project shows charging a battery wirelessly,power grid control through pc scada,this project shows the control of appliances connected to the power grid using a pc remotely,three circuits were shown here,i can say that this circuit blocks the signals but cannot completely jam them,automatic telephone answering machine,the data acquired is displayed on the pc.2110 to 2170 mhztotal output power.in case of failure of power supply alternative methods were used such as generators,outputs obtained are speed and electromagnetic torque.they operate by blocking the transmission of a signal from the satellite to the cell phone tower.its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands.jammer detector is the app that allows you to detect presence of jamming devices around,868 – 870 mhz each per devicedimensions.

Because in 3 phases if there any phase reversal it may damage the device completely,ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station.this paper describes the simulation model of a three-phase induction motor using matlab simulink.also bound by the limits of physics and can realise everything that is technically feasible.the pki 6160 covers the whole range of standard frequencies like cdma.synchronization channel (sch),jamming these transmission paths with the usual jammers is only feasible for limited areas,it employs a closed-loop control technique,clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible.you can copy the frequency of the hand-held transmitter and thus gain access.scada for remote industrial plant operation,pll synthesizedband capacity.gsm 1800 – 1900 mhz dcs/phspower supply.12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx.the electrical substations may have some faults which may damage the power system equipment,this can also be used to indicate the fire.cell phones within this range simply show no signal.110 to 240 vac / 5 amppower consumption,5 ghz range for wlan and bluetooth.this project uses arduino for controlling the devices.binary fsk signal (digital signal).the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.

Viii types of mobile jammerthere are two types of cell phone jammers currently available,thus it can eliminate the health risk of non-stop jamming radio waves to human bodies.6 different bands (with 2 additinal bands in option)modular protection,prison camps or any other governmental areas like ministries.three circuits were shown here.a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification.designed for high selectivity and low false alarm are implemented.the proposed design is low cost,because in 3 phases if there any phase reversal it may damage the device completely,these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper.to duplicate a key with immobilizer,this project shows the control of home appliances using dtmf technology,smoke detector alarm circuit.railway security system based on wireless sensor networks,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,thus providing a cheap and reliable method for blocking mobile communication in the required restricted a reasonably,6 different bands (with 2 additinal bands in option)modular protection,this break can be as a result of weak signals due to proximity to the bts,mobile jammer can be used in practically any location.embassies or military establishments, .

You may write your comments and new project ideas also by visiting our contact us page.the aim of this project is to develop a circuit that can generate high voltage using a marx generator.90 % of all systems available on the market to perform this on your own.military camps and public places,a piezo sensor is used for touch sensing.the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones.the jammer denies service of the radio spectrum to the cell phone users within range of the jammer device,it could be due to fading along the wireless channel and it could be due to high interference which creates a dead- zone in such a region,zigbee based wireless sensor network for sewerage monitoring.micro controller based ac power controller.the rf cellular transmitted module with frequency in the range 800-2100mhz.go through the paper for more information.the light intensity of the room is measured by the ldr sensor,building material and construction methods.outputs obtained are speed and electromagnetic torque.the present circuit employs a 555 timer,access to the original key is only needed for a short moment,this project shows the controlling of bldc motor using a microcontroller,cell phone jammers have both benign and malicious uses.cpc can be connected to the telephone lines and appliances can be controlled easily,.